Find research datasets worth reusing

opencc-zeroMar 2024View details →

Using protein isolation on elasmobranch blood plasma for ecological research and stable isotope analysis

Stable isotope analysis is a useful tool for studying the ecology of elasmobranchs. Analysis of elasmobranch blood plasma provides insight into an individual's ecology on a small temporal scale. However, plasma is a systemic transport vessel containing many dissolved constituents in variable amounts, which may bias analyses and ecological conclusions based on that data. In this study, we develop a new method of protein precipitation using ethanol and acetonitrile to isolate the protein fraction of plasma from Sandbar Sharks, and examine its effects on carbon and nitrogen stable isotope values. We also tested these solvent precipitations on bovine serum albumin as a control to assess the introduction of exogenous sources of C and N. Protein isolation resulted in a significant decrease in δ13C values and a significant increase in C:N compared to untreated plasma. Isolated proteins were not significantly different in δ15N value compared to untreated plasma. We observed no change in isotope composition in bovine serum albumin samples, indicating protein precipitation does not itself affect isotope analysis. These results suggest that the preparation of blood plasma is necessary for stable isotope analysis, to eliminate the biasing effects of other dissolved compounds. We find that solvent precipitation is an effective method of isolating proteins for stable isotope studies.

opencc-zeroMar 2024View details →

Data from: Stable isotope evidence for long-term stability of large-scale hydroclimate in the Neogene North American Great Plains

The Great Plains of North America host a stark climatic gradient, separating the humid and well-watered eastern US from the semi-arid and arid western US, and this gradient shapes the region's water availability, its ecosystems, and its economies. This climatic boundary is largely set by the influence of two competing atmospheric circulation systems that meet over the Great Plains—the wintertime westerlies bring dominantly dry air that gives way to moist, southerly air transported by the Great Plains Low-Level Jet in the warmer months. Climate model simulations suggest that, as CO2 rises, this low- level jet will strengthen, leading to greater precipitation in the spring, but less in the summer and, thus, no change in mean annual precipitation. Combined with rising temperatures that will increase potential evapotranspiration, semi-arid conditions will shift eastward, with potentially large consequences for the ecosystems and inhabitants of the Great Plains. We examine how hydroclimate in the Great Plains varied in the past in response to warmer global climate by studying the paleoclimate record within the Ogallala Formation, which underlies nearly the entire Great Plains and provides a spatially resolved record of hydroclimate during the globally warmer late Miocene. We use the stable isotopes of oxygen (δ18O) as preserved in authigenic carbonates hosted within the abundant paleosol and fluvial successions that comprise the Ogallala Formation as a record of past hydroclimate. Today, and coincident with the modern aridity gradient, there is a sharp meteoric water δ18O gradient with high (−6 to 0‰) δ18O in the southern Great Plains and low (−12 to −18‰) δ18O in the northern Plains. We find that the spatial pattern of reconstructed late Miocene precipitation δ18O is indistinguishable from the spatial pattern of modern meteoric water δ18O. We use a recently developed vapor transport model to demonstrate that this δ18O spatial pattern requires air mass mixing over the Great Plains between dry westerly and moist southerly air masses in the late Miocene—consistent with today. Our results suggest that the spatial extent of these two atmospheric circulation systems have been largely unchanged since the late Miocene and any strengthening of the Great Plains Low-Level Jet in response to warming has been isotopically masked by proportional increases in westerly moisture delivery. Our results hold implications for the sensitivity of Great Plains climate to changes in global temperature and CO2 and also for our understanding of the processes that drove Ogallala Formation deposition in the late Miocene.

opencc-zeroApr 2024View details →

Data from: Dietary partitioning among three cryptobentic reef fish mesopredators revealed by visual analysis, metabarcoding of gut content, and stable isotope analysis

Understanding how mesopredators partition their diet and the identity of consumed prey can assist in understanding the ecological role predators and prey play in ecosystem trophodynamics. Here, we assessed the diet of three common coral reef mesopredators; Pseudochromis flavivertex, Pseudochromis fridmani, and Pseudochromis olivaceus from the family Pseudochromidae, commonly known as dottybacks, using a combination of i) visual stomach content analysis, ii) stomach content DNA metabarcoding (18S, COI), and iii) stable isotope analysis (δ15N, δ13C). In addition, P. flavivertex is found in two distinct color morphs in the Red Sea, providing an opportunity to analyze intra-morph differences. These techniques revealed partitioning in the dietary composition and resource use among species. Arthropods comprised the main dietary component of P. flavivertex (18S > 60%; COI > 10%), and P. olivaceus (18S = 57.2%) while P. fridmani ingested predominantly mollusks (18S = 51.3%, COI = 24.6%). Despite being small predators, microplastics were found in the gut content of some of these fishes. Stable isotope analysis showed differences in species' isotopic niche breadth and trophic position. Pseudochromis olivaceus presented the largest isotopic niche (SEAC = 1.61‰2), while P. fridmani showed the smallest isotopic niche (SEAC = 0.45‰2) among species. Although the two techniques used for stomach content analysis did not show differences in the diet within color morphs of P. flavivertex, they differed in the isotopic niche and resource use. Despite our limited sampling, our findings provide evidence of species-specific differences in the trophic ecology of dottybacks and demonstrate their important role as predators of cryptic invertebrates and small fishes. This study highlights the importance of combining several approaches (short-term: visual analysis and DNA metabarcoding; and long-term: isotope analysis) when assessing the feeding habits of coral reef fish, as they provide complementary information necessary to delimit their niches and understand the role that small mesopredators play in coral reef ecosystems.

opencc-by-4.0Apr 2024View details →

Dataset: Testing for effects of growth rate on isotope trophic discrimination factors and evaluating the performance of Bayesian stable isotope mixing models experimentally: a moment of truth?

Discerning assimilated diets of wild animals using stable isotopes is well established where potential dietary items in food webs are isotopically distinct. With the advent of mixing models, and Bayesian extensions of such models (Bayesian Stable Isotope Mixing Models, BSIMMs), statistical techniques available for these efforts have been rapidly increasing. The accuracy with which BSIMMs quantify diet, however, depends on several factors including uncertainty in tissue discrimination factors (TDFs; Δ) and identification of appropriate error structures. Whereas performance of BSIMMs has mostly been evaluated with simulations, here we test the efficacy of BSIMMs by raising domestic broiler chicks (Gallus gallus domesticus) on four isotopically distinct diets under controlled environmental conditions, ideal for evaluating factors that affect TDFs and testing how BSIMMs allocate individual birds to diets that vary in isotopic similarity. For both liver and feather tissues, δ13C and δ 15N values differed among dietary groups. Δ13C of liver, but not feather, was negatively related to the rate at which individuals gained body mass. For Δ15N, we identified effects of dietary group, sex, and tissue type, as well as an interaction between sex and tissue type, with females having higher liver Δ15N relative to males. For both tissues, BSIMMs allocated most chicks to correct dietary groups, especially for models using combined TDFs rather than diet specific TDFs, and those applying a multiplicative error structure. These findings provide new information on how biological processes affect TDFs and confirm that adequately accounting for variability in consumer isotopes is necessary to optimize performance of BSIMMs. Moreover, they demonstrate experimentally that these types of models reliably characterize consumed diets when appropriately parameterized.

opencc-zeroNov 2021View details →

E-scape: consumer-specific landscapes of energetic resources derived from stable isotope analysis and remote sensing

Energetic resources and habitat distribution are inherently linked. Energetic resource availability is a major driver of the distribution of consumers, but estimating how much specific habitats contribute to the energetic resource needs of a consumer can be problematic. We present a new approach that combines remote sensing information and stable isotope ecology to produce maps of energetic resources (E-scapes). E-scapes project species-specific resource use information onto the landscape to classify areas based on energetic importance. Using our E-scapes, we investigated the relationship between energetic resource distribution and white shrimp distribution and how the scale used to generate the E-scape mediated this relationship. E-scapes successfully predicted the size, abundance, biomass, and total energy of a consumer in salt marsh habitats in coastal Louisiana, USA at scales relevant to the movement of the consumer. Our E-scape maps can be used alone or in combination with existing models to improve habitat management and restoration practices and have potential to be used to test fundamental movement theory.

opencc-zeroDec 2020View details →

Stable isotopes unravel the feeding mode-trophic position relationship in trematode parasites

<div class="WordSection1"> 1. Stable isotopes have been sporadically used over the last two decades to characterise host-parasite trophic relationships. The main reason for this scarcity is the lack of an obvious pattern in the ratio of nitrogen stable isotope values (δ15N) of parasites in comparison to their host tissues, which would be key to understand any host-parasite system dynamics. 2. To circumvent this, we focused on a single snail host, Zeacumantus subcarinatus, and three of its trematode parasites. 3. We used stable isotopes to investigate each host-trematode trophic relationship and shed light on the mechanisms utilised by the parasite to reroute its hosts' biomass. 4. All our trematodes were found to be 15N-enriched compared to their host, with their δ15N values strongly related to their feeding behaviours: passive vs active. It was possible to 'rank' these parasite species and assess their 'relative' trophic position using δ15N values. We also demonstrated that including a broader range of samples (e.g. host food and faeces, multiple parasite life stages) helped understand the metabolic mechanisms used by the various participants, and that using carbon stable isotope values and C:N ratios allowed to identify an important lipid requirement of these trematode parasites. Finally, we show how critical it is to not ignore parasitic infections as they can have a great influence on their host's trophic position. 5. We have shown that by focussing on a single host species and a single taxonomic group of parasites, we can remove a certain amount of variation recorded by broader isotope studies. We hope that these data will ultimately improve our ability to place parasites in food webs, and thus improve our understanding of the connections and interactions that dictate food web dynamics. </div>

opencc-by-4.0Jan 2022View details →

Year-round observations of stable carbon isotopic composition of diacids and related compounds in fine aerosols at Tianjin, North China – Data set

To better understand the origins and photochemical processing of water-soluble organic aerosols in the Tianjin region, North China, we studied the stable isotopic composition (δ13C) of diacids, oxoacids, α-dicarbonyls, citric acid and fatty acids in fine aerosols (PM2.5) collected at an urban (Nankai District, ND; n = 121) and a suburban (Haihe Education Park, HEP; n = 40) sites in Tianjin from 5 July 2018 to 4 July 2019. The δ13C of diacids and related compounds were measured using a capillary gas chromatography (Agilent 7890B) coupled with isotope ratio mass spectrometry (GC-irMS) system. Based on seasonal variations in δ13C of selected species and linear relations with their concentrations and mass ratios, we found that the diacids and related compounds were mainly derived from fossil fuel including coal combustion and biomass burning and photochemical processing, preferably in gaseous- and aqueous-phases in warm (March-September) and cold (October-February) periods, respectively, in Tianjin, North China.

opencc-by-4.0Feb 2022View details →

Stable Water Isotopes in Fresh Snow Along 2 Slopes in the canton of Grisons/Graubünden, Switzerland: the "Chruez", Praettigau and Eastward ascent to the Vilan Peak

This bachelor thesis concerned itself with the composition of \(\delta\)2H (or deuterium), \(\delta\)18O and \(\delta\)17O in fresh snow. Stable water isotopes have been proven to be useful tracers for hydrological processes, such as air mass sources of regional precipitation or the residence time of snowmelt in a catchment (Beria et al., 2018). Whereas different isotopic compositions of precipitation in the form of rain is well documented for different environments in networks such as the NISOT (The Swiss National Network for the Observation of Isotopes in the Water Cycle), the same knowledge about snow is more limited due to the influences of different isotope fractionation processes and lack of onsite snow accumulation and melt observation (Cooper, 1998; Michelon et al., 2018). The aim of this thesis was therefore to analyse and characterize the spatial variability of \(\delta\)2H, \(\delta\)18O and \(\delta\)17O in freshly fallen snow. This was done by sampling fresh snow on six different snowfall events in the month of March over an elevation gradient of 1000m along the southside slope of the mountain Chruez. 2H throughout four sampling days had \(\delta\)-values ranging from −50&permil; to −70&permil;, with two days being more depleted in 2H, showing \(\delta\)-values from −80&permil; down to −160&permil;. \(\delta\)18O showed the same pattern where of six, four days showed similar -values ranging from −8&permil; to −12&permil; and two days with a stronger depletion of the isotope with \(\delta\)-values ranging from −14&permil; to −20&permil;. It is known that the enrichment of \(\delta\)17O in a water molecule is about half of \(\delta\)18O, which was also seen in the results of this thesis (Nyamgerel et.al, 2021). In this thesis, two out of six sampling days were examined with statistically significant positive altitude gradients of 0.19&permil;/100m and 0.64&permil;/100m for \(\delta\)18O. Additionally, on one of the six sampling days, a statistically significant negative altitude gradient of −0.15&permil;/100m was observed. The altitude gradients for \(\delta\)17O were about half of \(\delta\)18O. Two statistically significant positive and one negative altitude gradients for \(\delta\)2H were observed during the same days with lapse rates of 1.7&permil;/100m, 5.5&permil;/100m and −1.25&permil;/100m. Having both positive and negative altitude gradients was attributed to the varying amounts of solar radiation and wind direction during different sampling days. However, further research must be done in order to make a valid statement, since additional factors such as water vapor pressure, turbulent fluxes in the air and relative humidity strongly affect fractionation of stable water isotopes. The aim of this work is to characterize and analyze the elevation effect of water isotopologues in fresh snow at Vilan. By analyzing fresh snow, the influence of fractionation processes, after the precipitation event can be minimized and helps the understanding of snow-melt water transformation. For this purpose, a total of five fresh snow events in March and April 2021 were analyzed. Samples were taken from the eastern slope of Vilan between 1100 m a.s.l. and 2300 m a.s.l. and were collected at 100-meter elevation intervals. The altitude effect was determined with a linear regression. The analysis shows that the altitude has only a small effect on the d-values of the new snow, because for the \(\delta\)18O only one snow event shows a statistically significant altitude effect. For the \(\delta\)2H, it is their two. The statistically significant new snow events show an elevation gradient of + 0.155 &permil; \(\delta\)18O/100 m and + 1.211 &permil; \(\delta\)2H/100 m and + 0.677 &permil; \(\delta\)2H/100 m, respectively. The observed positive gradients can be explained by four effects. First, a lee effect is likely due to the prevailing weather conditions. Second, the top snow layer accumulates heavy isotopologues with increasing time (time effect). Third, an inverse height effect can be observed when water vapor of different origins mixes. Fourth, the amount of precipitation (quantity effect) can have an impact on isotopic composition. The work shows that further research in the analysis of water isotopes in fresh snow is necessary to better identify and quantify possible influencing parameters.

opencc-by-4.0Feb 2022View details →

Aircraft profiles of stable isotope ratios in atmospheric total and condensed water from the NASA ORACLES mission.

Aircraft in-situ measurements of water concentration and heavy water isotope ratios D/H and 18O/16O of cloud water and total water (water vapor plus condensed water) were collected during the NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) project. Aircraft sampling took place in the southeast Atlantic marine boundary layer and lower troposphere (equator to 22 degrees south) over the months of Sept. 2016, Aug. 2017, and Oct. 2018. Isotope measurements were made using cavity ring-down spectroscopic analyzers integrated into the Water Isotope System for Precipitation and Entrainment Research (WISPER). The WISPER data are processed into mean latitude-altitude curtains and individual vertical profiles for each sampling period.   The WISPER data accompanied a suite of other variables including standard meteorological quantities (wind, temperature, moisture), trace gas and aerosol concentrations, radar, and lidar remote sensing, which can be accessed through the DOIs listed further down. The ORACLES campaigns are described by Redemann et al., (2021). The water isotope measurements are further described in Henze et al., (2021). The absolute error with respect to the SMOW-SLAP scale is explained in detail by Henze et al., (2021).   Total water concentration and isotope ratios were binned and averaged onto latitude-altitude grids using a kernel estimation approach, with weighting designed to estimate the mean during the approximate month-long duration of each sampling period. Standard deviations for each bin are also computed using kernel density estimation.   Time intervals during aircraft vertical profiling are isolated and averaged onto 50-meter vertical levels. The files include water concentration and isotope ratios for both total water and cloud water in addition to temperature, pressure, latitude, and longitude.   See included file README.txt for additional details.   References --------------- Henze, D., Noone, D., and Toohey, D.: Aircraft measurements of water vapor heavy isotope ratios in the marine boundary layer and lower troposphere during ORACLES, Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2021-238, in review, 2021.   Redemann, J., Wood, R., Zuidema, P., Doherty, S. J., Luna, B., LeBlanc, S. E., Diamond, M. S., Shinozuka, Y., Chang, I. Y., Ueyama, R., Pfister, L., Ryoo, J.-M., Dobracki, A. N., da Silva, A. M., Longo, K. M., Kacenelenbogen, M. S., Flynn, C. J., Pistone, K., Knox, N. M., Piketh, S. J., Haywood, J. M., Formenti, P., Mallet, M., Stier, P., Ackerman, A. S., Bauer, S. E., Fridlind, A. M., Carmichael, G. R., Saide, P. E., Ferrada, G. A., Howell, S. G., Freitag, S., Cairns, B., Holben, B. N., Knobelspiesse, K. D., Tanelli, S., L'Ecuyer, T. S., Dzambo, A. M., Sy, O. O., McFarquhar, G. M., Poellot, M. R., Gupta, S., O'Brien, J. R., Nenes, A., Kacarab, M., Wong, J. P. S., Small-Griswold, J. D., Thornhill, K. L., Noone, D., Podolske, J. R., Schmidt, K. S., Pilewskie, P., Chen, H., Cochrane, S. P., Sedlacek, A. J., Lang, T. J., Stith, E., Segal-Rozenhaimer, M.,  Ferrare, R. A., Burton, S. P., Hostetler, C. A., Diner, D. J., Seidel, F. C., Platnick, S. E., Myers, J. S., Meyer, K. G., Spangenberg, D. A., Maring, H., and Gao, L.: An overview of the ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) project: aerosol–cloud–radiation interactions in the southeast Atlantic basin, Atmos. Chem. Phys., 21, 1507–1563, https://doi.org/10.5194/acp-21-1507-2021, 2021.   The complete archive of ORACLES data are accessible via the digital object identifiers (DOIs) provided under ORACLES Science Team references as follows:   ORACLES Science Team: Suite of Aerosol, Cloud, and Related Data Acquired Aboard P3 During ORACLES 2018, Version 3, NASA Ames Earth Science Project Office, https://doi.org/10.5067/Suborbital/ORACLES/P3/2018_V3, 2020a.&ensp;   ORACLES Science Team: Suite of Aerosol, Cloud, and Related Data Acquired Aboard P3 During ORACLES 2017, Version 3, NASA Ames Earth Science Project Office, https://doi.org/10.5067/Suborbital/ORACLES/P3/2017_V3, 2020b.&ensp;   ORACLES Science Team: Suite of Aerosol, Cloud, and Related Data Acquired Aboard P3 During ORACLES 2016, Version 3, NASA Ames Earth Science Project Office, https://doi.org/10.5067/Suborbital/ORACLES/P3/2016_V3, 2020c.&ensp;   ORACLES Science Team: Suite of Aerosol, Cloud, and Related Data Acquired Aboard ER2 During ORACLES 2016, Version 3, NASA Ames Earth Science Project Office, https://doi.org/10.5067/Suborbital/ORACLES/ER2/2016_V3, 2020d.

opencc-by-4.0Apr 2022View details →

Data from: Condition-dependent immune function in a freshwater snail revealed by stable isotopes

Data are saved as a tab-delimited text file (data.txt). Each row represents one snail individual.   The file has the following columns: infection - trematode infection (0 = no, 1 = yes) PO_activity - PO-like activity of haemolymph antibacterial_activity - antibacterial activity of haemolymph shell_length - shell length (mm) faeces - amount of produced faeces (mg) d15N_faeces - δ15N value of faeces d13C_faeces - δ13C value of faeces C:N_faeces - C:N ration of faeces d15N_tissue - δ15N value of tissue d13C_tissue - δ13C value of tissue C:N_tissue - C:N ration of tissue

opencc-zeroApr 2022View details →

Tree-ring stable isotopes suggest an increase in Asian monsoon rainfall at 4.2 ka BP

A synthesis of stable oxygen isotope records from tree rings and speleothems does not support a significant hydroclimate transition in our study region around 4.2 ka, nor the notion that this rapid climate deterioration should be regarded as generalized climatic transition from the mid to late Holocene.

opencc-zeroMay 2022View details →

Concordant patterns of morphological, stable isotope, and genetic variation in a recent ecological radiation (Salmonidae:Coregonus spp.)

Groups of sympatric taxa with low inter-specific genetic differentiation, but considerable ecological differences, offer great opportunities to study the dynamics of divergence and speciation. This is the case of ciscoes (Coregonus spp.) in the Laurentian Great Lakes, which are characterized by a complex evolutionary history and are commonly described as having undergone an adaptive radiation. In this study, morphometrics, stable isotopes and transcriptome sequencing were used to study the relationships within the Coregonus artedi complex in western Lake Superior. We observed general concordance for morphological, ecological and genomic variation, but the latter was more taxonomically informative as it showed less overlap among species in multivariate space. Low levels of genetic differentiation were observed between individuals morphologically identified as C. hoyi and C. zenithicus, which could be evidence of incomplete lineage sorting or recent hybridization between the two groups. Transcriptome-based single nucleotide polymorphisms exhibited significant divergence for genes associated with vision, development, metabolism and immunity among species that occupy different habitats. This study highlights the importance of using an integrative approach when studying groups of taxa with a complex evolutionary history, as individual-level analyses of multiple independent datasets can provide a clearer picture of the patterns and processes associated with the origins of biodiversity.

opencc-zeroJun 2022View details →

Trophic structure and origin of resources of soil macrofauna in the salt marsh of the Wadden Sea: a stable isotope (15N,13C) study

Salt marshes exist along the gradient of the marine mudflat to the terrestrial dunes, with a gradient of shore height and associated plant zonation. The lower salt marsh (LSM) extends from the mean high tidal level to 35 cm above that level and is followed by the upper salt marsh (USM). Despite changes in the amount of allochthonous marine input and in abiotic conditions, little is known about changes in the trophic structure and used of basal resources by the soil macrofauna along marine – terrestrial boundaries. Natural variations in carbon stable isotope ratios (δ¹³C signatures) allow insight into basal resources of consumers such as marine algae, terrestrial C3 and C4 photosynthesising plants. Furthermore, variations in nitrogen stable isotope ratios (δ¹5N signatures) allow insight into the trophic position of consumers. We investigated spatial and temporal changes in stable isotope signatures in salt marsh soil macrofauna of the island of Spiekeroog, German Wadden Sea. The range of δ¹⁵N signatures indicated no changes in food chain length across salt marsh zones with consumers in both zones comprising primary decomposer, secondary decomposer and first order predators. However, the trophic position of individual species changed between zones, but in particular with season. Contrasting δ¹⁵N signatures, the range in δ¹³C signatures in the LSM was twice that in the USM indicating a wider range of resources consumed. Bayesian mixing models indicated predominant autochthonous resource use in both the LSM and USM, with the use of marine allochthonous resources never exceeding 29.6%. However, the models also indicate an increase in the use of marine resources in certain species in the LSM with no use in the USM. Overall, the results indicate that the resource use of salt marsh macrofauna varies more in space than in time, with the food web being generally based on autochthonous rather than allochthonous resources. However, there also is trophic plasticity in certain species across both temporal and spatial scales including variations in the use of allochthonous resources. Generally, however, marine input contributes little to the nutrition of salt marsh soil macroinvertebrates.

Data from: Stable isotopes in the different trophic levels reveal regional divergence in dietary habits among Tibetan pastoralists

Understanding geographical variation and driving mechanisms of the dietary habits of Tibetan pastoralists is a key to improving their health status under climate change and globalization. Characterization of diet via isotopic signatures along the length of the local food chain could provide this information. We analyzed δ13C and δ15N of soil, plants, animals and pastoralists at different geographical sites ranging in a gradient of easily accessible to remote areas. The high δ15N values in soil and plants were not recovered in animals and pastoralists, indicating use of external feed and food resources respectively. The mean δ13C (-22.0‰) and δ15N values (6.9‰) of pastoralists indicated diets consisting mainly of native C3 plants and animal products. Pastoralists living in the remotest areas maintained more traditional dietary habits based on native animal products. However, dietary changes of pastoralists were triggered by external food resources and alterations in ecological chain of easily accessible areas.

Diet analysis of David's deer (Elaphurus davidianus) based on stable isotope technology

Faecal stable isotopic analysis is now commonly used to investigate diets of mammal herbivores as samples are easy to obtain and reveal short-term dietary trends. In the Jiangsu Dafeng David's Deer National Nature Reserve, supplemental feed has been provided year round for free-ranging deer (Elaphurus davidianus) to survive from food shortages. Plant species are isotopically distinct in the free-ranging area. We assessed the plant species utilization by deer under supplemental feed condition. Diet-faeces trophic shift of deer was obtained in the semi-captive area. Faeces in both areas were collected and faecal δ13C values revealed more variable diets of free-ranging deer than semi-captive deer in different months. Mixing model showed that C4 plants were important food source for free-ranging deer when supplemental feed was provided. We suggest that efficiency and impacts of long-term supplemental feed should be considered for degraded habitat restoration.

Tracking Global Invasion Pathways of the Spongy Moth (Lepidoptera: Erebidae) to the U.S. using Stable Isotopes as Endogenous Biomarkers

The spread of invasive insect species causes enormous ecological damage and economic losses worldwide. A reliable method that tracks back an invaded insect's origin would be of great use to entomologists, phytopathologists and pest managers. The spongy moth (Lymantria dispar (L.d.), Linnaeus 1758) is a persistent invasive pest in the north-eastern United States (U.S.) and periodically causes major defoliations in temperate forests. We analysed field-captured (Europe, Asia, U.S.) and lab-reared L.d. specimens for their natal isotopic hydrogen and nitrogen signatures imprinted in their biological tissues (δ2H and δ15N) and compared these values to the long-term mean δ2H of regional precipitation (Global Network of Isotopes in Precipitation) and δ15N of regional plants at the capture site. We established the percentage of hydrogen-deuterium exchange for L.d. tissue (Pex=8.2%) using the comparative equilibration method and two-source-mixing-models, which allowed the extraction of the moth's natal δ2H value. We confirmed that the natal δ2H and δ15N values of our specimens are related to the environmental signatures at their geographic origins. With our regression models, we were able to isolate potentially invasive individuals and give estimations of their geographic origin. To enable the application of these methods on eggs, we established an egg-to-adult fraction factor for L.d. (Δegg-adult = 16.3‰ ± 4.3‰). Our models suggested that around 25% of the field-captured spongy moths worldwide were not native in the investigated capture sites. East Asia was the most frequently identified location of probable origin. Furthermore, our data suggested that eggs found on cargo ships in U.S. harbors in Alaska, California and Louisiana most probably originated from Asian L.d. in East Russia. These findings show that stable isotope biomarkers give a unique insight into invasive insect species pathways and thus, can be an effective tool to monitor the spread of insect pest epidemics.

Washington harbor seal stable isotope data

Understanding the response of predators to ecological change at multiple temporal scales can elucidate critical predator-prey dynamics that would otherwise go unrecognized. We performed compound-specific nitrogen stable isotope analysis (CSIA) of amino acids on 153 harbor seal museum skull specimens to determine how trophic position of this marine predator has responded to ecosystem change over the past century. The relationships between harbor seal trophic position, ocean condition, and prey abundance, were analyzed using hierarchical modelling of a multi-amino acid framework and applying 1-, 2-, and 3- year temporal lags. We identified delayed responses of harbor seal trophic position to both physical ocean conditions (upwelling, sea surface temperature, freshwater discharge) and prey availability (Pacific hake, Pacific herring and Chinook salmon). However, the magnitude and direction of the trophic position response to ecological changes depended on the temporal delay. For example, harbor seal trophic position was negatively associated with summer upwelling, but had a 1- year delayed response to summer sea surface temperature, indicating some predator responses to ecosystem change are not immediately observable. These results highlight the importance of considering dynamic responses of predators to their environment as multiple ecological factors are often changing simultaneously and can take years to propagate up the food web.

Stable-isotopes (δ2H, δ13C) within feathers from harvested American black ducks (2017-2020)

Stable isotope data from American Black Duck feathers (n = 665) and associated harvest data. The first primary feather (P1) was collected from wings submitted to the Species Composition Survey in Canada and Parts Collection Survey in the United States. From available feathers, we selected individuals for stable-isotope analysis stratified by black duck conservation region, sex, age, and date of harvest, where possible. These data are those that were selected for stable-hydrogen isotope analysis. See Kusack et al. (in press) - 'Origins of harvested American black ducks: stable isotopes support the flyover hypothesis' for additional information on our use of this data.

opencc-by-4.0Aug 2022View details →

Stable Isotope Hydrology Data from Gnamma Systems in the Colorado Front Range

This dataset accompanies a submission to Geophysical Research Letters titled "Stable Isotopes Constrain Water Seepage from Gnammas into Bare Granitic Bedrock".